We are dealing with a very barbaric organisation whose values are completely different from ours

Philip Hammond, Foreign Secretary

Mr Hammond assured his family the Government was doing all it could to help the former taxi driver from Salford, Greater Manchester.

But he added: “They understand, because we have explained to them in detail, the limitations of our abilities.

“We are dealing with a very barbaric organisation whose values are completely different from ours.”

He added: “We also cannot be deterred from our strategic objective of crushing ISIL (Islamic State) and the barbarous ideology it is trying to impose on the region”.

The Paris talks came amid expectations that David Cameron will say Britain is ready to join American air strikes when he speaks at the United Nations in New York next week.

The Prime Minister has resisted calls from some MPs to recall Parliament this week. Many think he could now call a sitting late next week.

Mr Cameron remains bruised by last year’s Commons defeat over a call for action against the regime in Syria.

But many MPs are now indicating they would back British involvement in targeted strikes against Islamic State jihadists.

France announced that its aircraft will join reconnaissance flights over Iraq, already being conducted by the RAF in support of US air strikes.

That follows an announcement at the weekend by Australian prime minister Tony Abbot that his country would be the first to commit troops to a US-led coalition fighting the extremists.

More than 30 foreign minister met today to discuss the response to IS [AP]

Speaking of the “death cult” of radical Islam, he warned that the looming fight could take “many, many months”. More than 600 Australian troops will be made available within days.

The meeting in Paris included representatives of the US and Russia as well as 10 Middle Eastern states.

Mr Hammond promised his counterparts that Britain would play “a leading role” in the coalition. But he said there had been no decision on what the UK would actually do.

He would not be drawn on whether we will join air strikes in Syria as well as in Iraq.

Coalition planes operating over Syria would run the risk of attacks by the forces of President Bashar Assad.

“It would be more difficult than strikes in Iraq for all sorts of reasons, military, legal and technical, but we haven’t ruled it out,” Mr Hammond said.

Downing Street said the international strategy was to build support for Iraqi and Kurdish forces, who were the right people to lead combat efforts on the ground.

Home Secretary Theresa May condemned the “barbaric” murder of Mr Haines, 44.

She told an audience in the US: “The United Kingdom, like the United States, will not allow these grotesque acts to stop us from keeping our homelands secure and stopping the march of this brutal ideology.”